Okay, so imagine you have a big box of all your toys and you put them in there to keep them safe. You can open the box any time and take out the toys you want to play with.
Now imagine that instead of toys, you have really old papers and documents that people wrote a long time ago. These papers are really important because they tell us about history and how people used to live.
An open archive is like a big box that people put these old papers and documents in. But it's not just any box, it's a special box that everyone can look in and learn from.
So, if you're curious about history and want to learn something new, you can go to an open archive and look at the old papers and documents that people have put in there. It's like a big library of information that's available for everyone to learn from.